Buying together without marrying in Thailand: why an unmarried partner inherits nothing

If my partner and I aren't married, what happens to our Koh Phangan property if one of us dies, or we split up? Under Thai law, nothing happens automatically in the partner's favor — because Thailand recognizes no common-law or de facto marriage, no matter how many years a couple has lived together, shared expenses, or jointly funded a villa. Only a marriage registered at the district (Amphur) office under Civil and Commercial Code Section 1457 creates a legal spouse. Everything this site has already covered on protecting a spouse's interest, a prenuptial agreement, and same-sex marriage property rights depends on that registration having happened — an unmarried couple, opposite-sex or same-sex, sits entirely outside all of it.

Inheritance defaults to zero for an unmarried partner

As dying without a will in Thailand already covers, Civil and Commercial Code Sections 1629 and 1635 set a strict order of statutory heirs — descendants, parents, siblings, and so on — with a registered spouse inheriting alongside them. An unmarried partner appears nowhere on that list. If one partner dies without a will, the survivor has no automatic claim at all to a villa, lease, or company shares titled in the deceased's name, regardless of how the purchase was actually funded — the property passes to the deceased's blood relatives (or, absent any, to the state) instead.

Separation is not divorce — there's no marital-property regime to divide

A registered marriage triggers Thailand's marital-property rules on divorce; an unmarried breakup triggers nothing comparable. Property bought during the relationship isn't automatically joint just because a couple lived together while acquiring it — Thai courts have instead applied ordinary co-ownership principles on a case-by-case basis, requiring the claiming partner to prove an actual financial or in-kind contribution to the specific asset. That's a materially heavier burden of proof than a registered spouse faces, and it produces no guaranteed outcome.

What actually protects an unmarried partner

• A Thai will naming the partner as legatee. Thailand has no forced-heirship rule blocking this the way some civil-law jurisdictions do — see the legal forms a Thai will can take — so a will is the single most direct fix for the inheritance gap, and it costs far less than any dispute after the fact.
• A registered usufruct, right of habitation, or superficies granted directly to the partner. These are available regardless of marital status — see superficies vs usufruct vs lease — and, unlike an unregistered claim, bind the property and survive a change of registered owner.
• Joint registration on a lease, or joint shareholding in a property-holding company, gives each partner their own registered interest instead of relying on inheriting the other's.
• A written cohabitation agreement, drafted and signed like any other civil contract. Thai courts have enforced these and have applied co-ownership principles guided by one, but a cohabitation agreement does not itself transfer title or substitute for a will — it only helps prove what each partner actually contributed if a dispute over separation ever reaches court.
• None of this expands what a foreign partner can hold. The Land Code's restrictions on foreign land ownership apply exactly the same to an unmarried foreign partner as to a foreign spouse — a usufruct, superficies, lease, or company structure is still the mechanism, not direct foreign freehold title.

The practical takeaway: registering a marriage is the only step that brings Thailand's statutory spousal-inheritance and marital-property protections into play at all — everything short of that, gender aside, is legally a stranger's claim unless the couple has actively built protections in with a will, a registered interest, and ideally a written agreement, well before either becomes necessary.