i buy my ipad in thailand and lost receipt

Contact the store and see if they are able to email it to you. If you used your email address when purchasing the device, they already have it on file.

See if this works: https://macreports.com/how-to-find-receipts-for-apple-purchases/

Contacting the store would likely be done by a phone call. An email may be available if the store has a web page on the internet for customer service, but not always.