Contents
Plan
Status: first draft, 27 Sep 2026, revised 21 Oct 2026 for the
operating model (operating-model.md),
shared utilities (utilities.md) the gate
and guards (security-and-access.md) and the
layout with gardens, a natural park, the club and a water tower (site-plan.md); revised 3 Nov 2026 for the
corner houses (Type C, with a private pool), the perimeter trail, the
green lanes and the fitness stations, which take the 14-house flagship
to 16.9 rai. Dates are targets, costs are estimates from model/cost_model.py.
Bracketed numbers such as [5]
refer to sources.md.
Strategy in one paragraph
Do not buy 16.9 rai first. The engineering is not the risk; the rent is. A premium Type A house that the estate also runs for its tenant needs about 80,000 to 144,000 THB a month all-inclusive for a 5 % net yield, and the corner Type C about 194,000 (costs-and-rent.md), while normal new 3-bed estate houses let for 20,000 to 38,000 and only branded lakeside or pool houses reach 55,000 to 90,000.[5][6] So the plan proves four things cheaply and in order (the air works, tenants pay for the whole package, we can build it at the modelled cost, we can run it at the modelled cost), and commits the big capital only after each one is proven.
Phases and gates
| Phase | When | What | Spend (est.) | Gate to pass before the next phase |
|---|---|---|---|---|
| 0. Decide | Oct 2026 to Jan 2027 | Owner entity and land-holding structure with a Thai lawyer; budget ceiling; tax class of rental houses; lease templates for short and long leases under the 2025 consumer protection rules;[30] written opinion on supplying tenants through the estate grid;[35] PEA: tariff class of one 22 kV connection and whether the estate may export;[33][34] groundwater licence route;[36] contracted vs in-house guards under the Security Business Act,[48] CCTV privacy notice and retention periods | ~0.2 M | Structure agreed; investor accepts a 4 to 5 % net target on all-inclusive rent; grid-supply opinion says the shared grid is allowed, or the fallback (a PEA meter per house) is chosen |
| 1a. Smoke-season test | Jan to Apr 2027 | Lease one existing house, seal it, fit a ducted HEPA supply at overpressure, log indoor vs outdoor PM2.5 with B4L AQI sensors | ~0.3 M | Indoor PM2.5 ≤ 12 µg/m³ on days outdoor > 75; data usable in marketing |
| 1b. Design and prices | Oct 2026 to Mar 2027 | Architect + MEP + structure for Types A, B and C; hourly energy
model replacing the estimates in model/estate_energy.py;
shared grid, battery and water plant designed; quantity survey; 3 quotes
per system, including the Type C private pools; Passive House certifier
and blower-door contractor found; full-service plan priced (team,
contracts, spares); guards quoted by two or three Chiang Mai security
companies; gate, intercom and CCTV quoted as one package by an
integrator who also services it |
~1.3 M (pilot soft costs) | Quoted cost within +10 % of model (Type A spec upgrades ≤ 3.19 M, Type C with its pool ≤ 5.72 M); running-cost plan, guards included, within +10 % of the model |
| 1c. Rent test | Jan to Apr 2027 | Show the design, the section, the service promise and the smoke-season data to relocation agents, the Hang Dong schools' HR, consulates, NGOs; ask for pre-lease letters of intent | ~0.05 M | Two LOIs at ≥ 65,000 THB/month all-inclusive for 2 to 3 years |
| 2. Pilot build | May 2027 to Apr 2028 | Buy or lease ~0.6 rai serviced plot in Hang Dong; build 2 Type A houses on one shared connection with a 30 kWh battery and one shared water supply and booster set, so the shared utilities are tested at small scale; both houses get the estate's intercom, with the plot gate calling the houses directly; B4L runs QA against spec.md §8 | ~23.0 M total for 2 houses incl. land | Both houses pass blower-door (n50 ≤ 0.6), electrical, plumbing and islanding tests; final cost within +10 % |
| 3. Pilot in use | May 2028 to Apr 2029 | Let both houses on full-service leases; measure energy, PM2.5, comfort, every service hour and cost, through the 2029 smoke season | Operating | Achieved rent ≥ 90 % of the model rent; ≤ 1 month vacancy; measured energy ≤ 550 kWh/month per house; measured full-service cost within +15 % of the model |
| 4. Estate go / no-go | May 2029 | Update the model with real costs, rents and service costs; choose flagship (16.9 rai, 14 houses incl. 4 Type C) or lean (6.5 rai, 12 houses); land option signed earlier in phase 3 | Land 16 to 81 M (part of the phase 5 total) | Investor approval on real numbers |
| 5. Estate build | 2029 to 2031 | Infrastructure and utilities first (grid, battery, standby generator, water plant and water tower, sewage, ring road, stormwater tank, wall and gate, perimeter trail), then houses row by row, letting each row as it completes, with the natural park, the trail and the club open for the first tenants; technical team hired and guard contract signed before the first row is let | 155 to 310 M all-in, incl. land | Per-row: same tests as the pilot |
Phases 0, 1a, 1b and 1c run in parallel, so by April 2027 the project has its answers (is it allowed, does the air work, what does it really cost, will anyone pay) for roughly 1.9 M THB, before any land is bought.
Why a pilot of two, not one
Two identical houses side by side give a real cost number (the second one shows the learning curve), a like-for-like pair for testing variants (for example an allowance against metered electricity), a two-house version of the shared grid and water supply, and one house can be the show house while the other is let.
Who is involved
| Role | Who | Notes |
|---|---|---|
| Owner / investor | [to decide in phase 0] | Thai company or lease structure; foreigners cannot hold land directly;[22] owns land, houses and utilities, never sells house by house |
| Specification, QA, monitoring | B4L | spec.md, B4L construction-standards, AQI sensors, Home Assistant, commissioning and house passports |
| Estate operations | B4L sets it up | Technical team (lead technician, technician, shared facilities engineer), workshop and spares, service contracts, dashboard (operating-model.md); guard contract and gate procedures (security-and-access.md) |
| Security company | Licensed contractor, Chiang Mai | Gate post 24 h and night patrol; licensed guards, background checks, the estate's service training[48] |
| Architect | Chiang Mai practice with tropical passive design experience | Brief: this concept, the section, the spec |
| MEP, energy and utilities engineer | Independent engineer | Hourly model for cooling load, ERV sizing; shared grid, battery and islanding; water plant and ring main |
| Passive House certifier | Accredited certifier | PHPP review and certificate per house |
| Structural engineer | Licensed in Thailand | Zone 3 seismic design,[24] soil tests |
| Contractor | Design-build or general contractor with B4L QA holds | Airtightness is new to most Thai trades: training day and a mock-up wall before the first house |
| Leasing | Relocation agents, school HR, direct corporate leases | Price against premium estates and pool villas, not estate houses; sell the service, not only the house |
| Legal and tax | Thai property lawyer | Entity, land title, lease templates under the 2025 rules,[30] long-lease registration,[31] grid-supply opinion,[35] land and building tax class[25] |
Permits and rules (to confirm with the lawyer in phase 0)
- Building permit per house (Building Control Act), with the Zone 3 seismic design.[24]
- Keep the estate on one title and rent every house. Selling ten or more sub-parcels counts as land allocation under the Land Allocation Act and needs a licence;[29] allocators also carry infrastructure maintenance obligations backed by bank guarantees under the 2569 amendment.[21]
- Leases. The 2025 consumer protection notification covers lessors with three or more residential units: Thai-language contracts, deposits and advance rent capped, no rent increase during the term, utilities at no more than official tariffs.[30] Leases longer than 3 years must be registered at the Land Office and are capped at 30 years.[31] No nightly or weekly lets: the Hotel Act excludes only accommodation let monthly or longer.[32]
- Electricity. One PEA 22 kV connection with an estate transformer; PV under 1 MW for self-consumption needs PEA interconnection approval and a building modification permit but no ERC licence;[34] tariff class and export to be confirmed with PEA;[33] whether supplying tenants through the estate grid needs an ERC licence needs a written opinion.[35]
- Water. Drilling and use licences for wells deeper than 15 m; in Chiang Mai they are issued by the municipality or tambon office.[36] Or a PWA connection where available.
- Estate sewage treatment and drainage approval with the local administration (tambon / municipality); confirm whether any environmental screening applies at the chosen site and size.
Main risks
| Risk | Mitigation |
|---|---|
| Tenants will not pay 80,000 to 144,000 THB/month all-inclusive (Type C 194,000) for a spec and a service they cannot see | Phase 1a data and a live PM2.5 dashboard in the show house; the service promise in writing; corporate LOIs before the pilot build; metered-electricity variant lowers the rent by about 2,700 |
| Chiang Mai housing oversupply (4+ years of stock)[20] | Rent, do not sell; target a segment that the stock does not serve (clean air, verified quality, no repairs) |
| Supplying tenants through a private grid needs an ERC licence[35] | Written opinion in phase 0; fallback is a PEA meter per house with its PV behind it (costs about 0.05 to 0.3 M THB a year more for the flagship, utilities.md); the water plant stays shared |
| The central water plant or grid fails and every house loses water or power | Two transfer pumps, two wells, a water tower that holds about four days and supplies by gravity with every pump stopped; looped main and cable ring with section valves and a normally-open point; battery backup; spares in the estate store; 1-hour response target |
| Full service costs more than modelled | Pilot measures every service hour and part; one model per system; ±25 % on service costs moves the flagship rent by about ±6,900 THB/month |
| Rent fixed for the whole lease; tenants may leave after half the term[30] | Standard leases of 2 to 3 years with renewal; long leases only with steps the lawyer confirms are allowed; one month of vacancy a year in the model |
| Thai trades cannot deliver Passive House airtightness and clean insulation details | Mock-up wall, training, B4L QA holds, pre-plaster blower-door test on every house |
| Cost overrun on imported windows, ERV, battery | Three quotes each in phase 1b; design allows two approved window systems; 10 % contingency (15 % in the sensitivity costs 3,200 THB/month of flagship rent) |
| Flood | Site screening against 2024 flood extents[19] and the Ping River monitor history; fill + plinth + a closed stormwater tank and a dry detention lawn (no open water) |
| The estate cannot export solar | Base case assumes no export: 6 kWp per house is near the no-export optimum and roofs are ready for 10 kWp if export is allowed later |
| Land title or entity structure fails due diligence | Phase 0 before any deposit; land option rather than purchase until phase 4 |
| A 24-hour guard post is expensive for 12 to 14 houses (about 3,400 to 4,000 THB per house per month for the gate post alone) | Local quotes in phase 1b; the night patrol is optional; prefer the flagship size, or a site where the gate can be shared with a neighbouring development |
Decisions needed now
- Is a 4 to 5 % net yield on a premium, long-life, all-inclusive rental asset acceptable to the investor? If the answer is "6 % or nothing", this concept does not work in Chiang Mai at today's rents.
- Approve phase 0 and phases 1a to 1c (about 1.9 M THB) to get the answers by April 2027.
- Who owns it: which entity, and is B4L the specifier and QA party only, or also the developer and the estate operator?
- What the rent includes: electricity and water allowances in the rent (base case), or electricity metered and billed per kWh (about 2,700 THB/month lower rent on the flagship).
- Long leases: offer registered leases of more than 3 years (up to 30) from the start, or only 1 to 3 year leases until the lawyer settles how rent can follow costs.
- Solar size: 6 kWp fitted with every roof ready for 10 kWp (base case), or full 10 kWp from day one, which only pays if PEA confirms the estate can export.
- Visitors: the guard calls the house for every visitor and delivery (base case), or tenants may also book guests in advance with a temporary pass that the guard checks instead of calling (security-and-access.md).
- Guards on the flagship: a 24-hour gate post plus a night patrol (base case), or the gate post alone with the perimeter watched by cameras (about 2,000 THB/month lower rent).