fix: post customer withholding as a Deduct tax row, not a deduction

With a deduction row ERPNext treats Paid Amount as cash received and
credits the party for paid + deduction, so a gross Paid Amount (what Get
Outstanding Invoices fills) over-credited Debtors and posted the gross
to the bank. Use the taxes table with add_deduct_tax=Deduct like
supplier TDS: Paid Amount is the gross settlement, bank receives paid
minus withholding, receivable is debited. Override Payment Entry
build_gl_map to flag the bank entry post_net_value so the merged bank
line shows the net amount.

default_thai_company/tax_withholding.py

@@ -1,5 +1,6 @@
 import erpnext
 import frappe
+from erpnext.accounts.doctype.payment_entry.payment_entry import PaymentEntry
 from erpnext.accounts.doctype.sales_invoice.sales_invoice import SalesInvoice
 from erpnext.accounts.doctype.tax_withholding_category.tax_withholding_category import (
 	get_tax_withholding_details,
@@ -157,15 +158,31 @@ class ThaiSalesInvoice(SalesInvoice):
 			)
 
 
+class ThaiPaymentEntry(PaymentEntry):
+	def build_gl_map(self):
+		"""A "Deduct" tax row on a receipt posts bank Dr gross and bank Cr
+		withholding; ERPNext merges them into one entry but only nets it when
+		the bank entry itself carries `post_net_value`. Set it so the bank
+		ledger shows the amount that actually arrived."""
+		gl_entries = super().build_gl_map()
+		if self.payment_type == "Receive" and self.party_type == "Customer" and self.get("taxes"):
+			for entry in gl_entries:
+				if entry.account == self.paid_to:
+					entry.post_net_value = True
+		return gl_entries
+
+
 def set_customer_withholding(doc, method=None):
 	"""Payment Entry.validate: tax withheld by the customer on a Receive entry
-	becomes a deduction to the company's withholding receivable account.
+	is posted like ERPNext's supplier TDS, as a "Deduct" row in the taxes
+	table against the withholding receivable account.
 
-	Withholding is rate x pre-VAT amount of each allocated reference, prorated
-	by the allocation. `paid_amount` is the cash actually received, so the
-	deduction closes the difference against the gross allocation. Runs after
-	the controller's validate (exchange rates and allocations are final), then
-	re-derives the two amounts that depend on deductions.
+	`paid_amount` is the gross amount settled against the invoices (what
+	"Get Outstanding Invoices" fills in); the bank receives paid minus the
+	withholding (`received_amount_after_tax`). Withholding is rate x pre-VAT
+	amount of each allocated reference, prorated by the allocation. Runs after
+	the controller's validate, then re-runs the tax computation so the row's
+	base amounts and totals are final within this save.
 	"""
 	if doc.party_type != "Customer" or doc.payment_type != "Receive" or not doc.apply_tax_withholding_amount:
 		return
@@ -181,20 +198,22 @@ def set_customer_withholding(doc, method=None):
 		frappe.throw(_("Account {0} not found for Company {1}").format(ASSET_ACCOUNT, doc.company))
 
 	amount, description = get_customer_withholding(doc)
-	row = next((d for d in doc.deductions if d.account == account), None)
+	row = next((d for d in doc.taxes if d.account_head == account), None)
 
 	if not amount:
 		if row:
 			doc.remove(row)
 	else:
 		if not row:
-			row = doc.append("deductions", {"account": account})
-		row.amount = amount
+			row = doc.append(
+				"taxes", {"account_head": account, "charge_type": "Actual", "add_deduct_tax": "Deduct"}
+			)
+		row.tax_amount = amount
 		row.description = description
 		row.cost_center = doc.cost_center or erpnext.get_default_cost_center(doc.company)
 
-	doc.set_unallocated_amount()
-	doc.set_difference_amount()
+	doc.apply_taxes()
+	doc.set_amounts_after_tax()
 
 
 def get_customer_withholding(doc):