What should I do if I lost my passport with all visas and extensions while outside Thailand?

If you've lost your passport that contained a re-entry permit and all visas/extensions while outside Thailand, the first step is to report the loss to the police and then contact your embassy to apply for a new passport or an emergency travel document. Depending on your nationality, some embassies may issue emergency passports, but it's important to check if Thailand accepts them. Once you have a new passport, you will need to apply for a new visa to return to Thailand.