While there are currently no laws making commercial surrogacy illegal in Thailand, some are in the works. The Department of Foreign Affairs and Trade warns Australians that:
The legal situation regarding surrogacy arrangements in Thailand is currently unclear. There is presently no legislation in Thailand which specifically regulates surrogacy. The Thai authorities are considering draft legislation that may prohibit commercial surrogacy. The Australian Government is encouraging Thai authorities to adopt transitional arrangements for any new measures they may introduce so that concerned Australians are not unduly affected.
Current advice is that Thai authorities are enforcing documentation requirements upon exit of the country when they suspect a child has been born by surrogacy in Thailand. Australians with existing agreements who may be affected by these arrangements should call the Consular Section at the Australian Embassy in Bangkok for latest information (Tel: +66 2 344 6300 and follow the prompts for Consular Services).
We strongly recommend that Australians visiting Thailand for the purposes of commercial surrogacy arrangements seek independent legal advice before doing so. In particular, legal advice should be sought on the implications of any new exit requirements. You should also see our Overseas births, adoptions and surrogacies page for further information.
Familiarise yourself with the current travel advisory for Thailand from DFAT here: http://www.smartraveller.gov.au/zw-cgi/view/Advice/Thailand