feat: Social Security deduction component

Employee's Social Security Fund contribution (Sec. 33): 5% of wages,
wages taken as at least 1,650 and at most 17,500 a month (2026-2028
ceiling), fractions of a baht rounded half up. Computed from the Basic
earning rather than `base` so a partial month is 5% of the wages
actually paid and the ceiling applies after proration. The contribution
is deductible from taxable income in full, so the component is
exempted_from_income_tax. Withheld amounts are held in "Social Security
Payable" (ประกันสังคมค้างจ่าย) until remitted.

Created once a Thai company exists (Company.on_update, install hooks,
scheduler, the setup_salary_components patch); the Salary Component
validate hook links every Thai company.

default_thai_company/hooks.py

@@ -236,6 +236,10 @@ doc_events = {
 			"default_thai_company.payroll.setup_company",
 		],
 	},
+	# HRMS doctype; the hook only fires on sites that have it.
+	"Salary Component": {
+		"validate": "default_thai_company.payroll.set_component_accounts",
+	},
 	"Payment Entry": {
 		"validate": "default_thai_company.tax_withholding.set_customer_withholding",
 	},

default_thai_company/patches.txt

@@ -8,3 +8,4 @@ default_thai_company.patches.create_vat_accounts
 default_thai_company.patches.create_vat_templates
 default_thai_company.patches.create_shipping_rules
 default_thai_company.patches.create_payroll_periods
+default_thai_company.patches.setup_salary_components

default_thai_company/patches/setup_salary_components.py

@@ -0,0 +1,5 @@
+from default_thai_company.payroll import setup_companies
+
+
+def execute():
+	setup_companies()

default_thai_company/payroll.py

@@ -1,18 +1,102 @@
 import frappe
 from frappe.utils import getdate
 
-from default_thai_company.tax_withholding import thai_companies
+from default_thai_company.tax_withholding import get_or_create_account, thai_companies
 
 # Thai personal income tax (P.N.D.1/91) is assessed per calendar year whatever
 # the company's fiscal year, so the Payroll Period is January to December.
 # Payroll Period is named by prompt (site-wide unique) but bound to one company,
 # so each Thai company gets "<year> - <abbr>", like the Shipping Rule.
+#
+# Payroll Entry refuses to post a component without an account for its company,
+# so every Salary Component gets one for every Thai company (Salary
+# Component.validate for the components HRMS seeds with the first company and
+# the ones users add; Company.on_update for companies added later).
+# Earnings expense to "Salary" (Standard chart, Indirect Expenses). The income
+# tax component is tax withheld from employees, remitted on P.N.D.1; Thai books
+# carry it as ภาษีหัก ณ ที่จ่ายค้างจ่าย, split by return form when split at all,
+# so it gets its own withholding account beside the P.N.D.3/53 one the Tax
+# Withholding Categories post to. Other deductions (social security, loans)
+# are held in "Salary Deductions" (Current Liabilities) until remitted.
+EARNING_ACCOUNT = "Salary"
+EARNING_ACCOUNT_GROUPS = ("Indirect Expenses", "Expenses")
+INCOME_TAX_ACCOUNT = "Withholding Tax Payable (P.N.D.1)"
+DEDUCTION_ACCOUNT = "Salary Deductions"
+DEDUCTION_ACCOUNT_GROUPS = ("Current Liabilities",)
+
+# Employee's Social Security Fund contribution (Sec. 33): 5% of wages, wages
+# taken as at least 1,650 and at most 17,500 a month (2026-2028 ceiling; 20,000
+# from 2029), fractions of a baht rounded half up. Computed from the Basic
+# earning rather than `base` so a partial month is 5% of the wages actually paid
+# and the ceiling applies after proration, as the Social Security Office
+# assesses it. The contribution is deductible from taxable income in full, so
+# the component is exempted_from_income_tax; the "Social Security Fund"
+# exemption sub-category is for contributions not run through payroll here.
+# The employer's equal share is not an employee deduction and is left to the
+# accounts. Thai books carry the withheld amount as ประกันสังคมค้างจ่าย until
+# it is remitted by the 15th, so it gets its own liability.
+SOCIAL_SECURITY_COMPONENT = {
+	"doctype": "Salary Component",
+	"salary_component": "Social Security",
+	"salary_component_abbr": "SSO",
+	"type": "Deduction",
+	"description": "Social Security Fund contribution (Sec. 33 employee)",
+	"depends_on_payment_days": 0,
+	"exempted_from_income_tax": 1,
+	"condition": "B > 0",
+	"amount_based_on_formula": 1,
+	"formula": "int((1650 if B < 1650 else 17500 if B > 17500 else B) * 5 / 100 + 0.5)",
+}
+SOCIAL_SECURITY_ACCOUNT = "Social Security Payable"
 
 
 def hrms_installed():
 	return "hrms" in frappe.get_installed_apps()
 
 
+def salary_component_account(company, component):
+	if component.type == "Earning":
+		return get_or_create_account(company, EARNING_ACCOUNT, "Expense", "", EARNING_ACCOUNT_GROUPS)
+	if component.is_income_tax_component:
+		return get_or_create_account(company, INCOME_TAX_ACCOUNT, "Liability")
+	if component.salary_component == SOCIAL_SECURITY_COMPONENT["salary_component"]:
+		return get_or_create_account(
+			company, SOCIAL_SECURITY_ACCOUNT, "Liability", "", DEDUCTION_ACCOUNT_GROUPS
+		)
+	return get_or_create_account(company, DEDUCTION_ACCOUNT, "Liability", "", DEDUCTION_ACCOUNT_GROUPS)
+
+
+def link_company(component, company):
+	"""Append the company's account row to the component if missing. Statistical
+	components never post, so they get none."""
+	if component.statistical_component or any(row.company == company for row in component.accounts):
+		return False
+	component.append(
+		"accounts", {"company": company, "account": salary_component_account(company, component)}
+	)
+	return True
+
+
+def set_component_accounts(doc, method=None):
+	"""Salary Component.validate: an account for every Thai company."""
+	for company in thai_companies():
+		link_company(doc, company)
+
+
+def ensure_component_accounts(company):
+	for name in frappe.get_all("Salary Component", pluck="name"):
+		component = frappe.get_doc("Salary Component", name)
+		if link_company(component, company):
+			component.save(ignore_permissions=True)
+
+
+def ensure_social_security_component():
+	"""Social Security deduction; the validate hook links every Thai company."""
+	if frappe.db.exists("Salary Component", SOCIAL_SECURITY_COMPONENT["salary_component"]):
+		return
+	frappe.get_doc(SOCIAL_SECURITY_COMPONENT).insert(ignore_permissions=True)
+
+
 def payroll_period_name(company, year):
 	abbr = frappe.get_cached_value("Company", company, "abbr")
 	return f"{year} - {abbr}"
@@ -39,24 +123,32 @@ def ensure_payroll_period(company, year):
 
 
 def setup_company(doc, method=None):
-	"""Company.on_update: this year's Payroll Period for a Thai company."""
+	"""Company.on_update: this year's Payroll Period, the Social Security
+	component and the Salary Component accounts for a Thai company."""
 	if doc.country == "Thailand" and hrms_installed():
 		ensure_payroll_period(doc.name, getdate().year)
+		ensure_social_security_component()
+		ensure_component_accounts(doc.name)
 
 
 def setup_companies():
-	"""after_install, the daily scheduler, and the create_payroll_periods patch:
-	this year's Payroll Period for every Thai company. The scheduler rolls the
-	default over on 1 January."""
+	"""after_install, the daily scheduler, and the setup_salary_components
+	patch: this year's Payroll Period, the Social Security component and the
+	Salary Component accounts for every Thai company. The scheduler rolls the
+	Payroll Period over on 1 January."""
 	if not hrms_installed():
 		return
 	year = getdate().year
-	for company in thai_companies():
+	companies = thai_companies()
+	if companies:
+		ensure_social_security_component()
+	for company in companies:
 		ensure_payroll_period(company, year)
+		ensure_component_accounts(company)
 
 
 def after_app_install(app_name):
-	"""Payroll Period only exists once hrms is installed; catch companies that
-	were created before it."""
+	"""Payroll Period and Salary Component accounts only exist once hrms is
+	installed; catch companies that were created before it."""
 	if app_name == "hrms":
 		setup_companies()

default_thai_company/translations/th.csv

@@ -74,6 +74,11 @@ Rounded Total,ยอดรวมปัดเศษ
 Terms and Conditions Details,รายละเอียดข้อตกลงและเงื่อนไข
 Page {0} of {1},หน้า {0} จาก {1}
 Withholding Tax Payable,ภาษีหัก ณ ที่จ่ายค้างจ่าย
+Withholding Tax Payable (P.N.D.1),ภาษีหัก ณ ที่จ่ายค้างจ่าย (ภ.ง.ด.1)
+Salary Deductions,รายการหักจากเงินเดือน
+Social Security,ประกันสังคม
+Social Security Payable,ประกันสังคมค้างจ่าย
+Social Security Fund contribution (Sec. 33 employee),เงินสมทบกองทุนประกันสังคม (ผู้ประกันตนมาตรา 33)
 Withholding Tax Receivable,ภาษีถูกหัก ณ ที่จ่าย
 Output VAT,ภาษีขาย
 Input VAT,ภาษีซื้อ