19 hours ago, ubonjoe said:

I most cases the old passport would be cancelled when the new one is issued. In the OP's case his home country does not cancel a replacement passport. He stated he is a allowed to have up to 3 valid passports.

Yes, not even the Embassy in Bangkok can cancel my passport. It has to be sent back to my country.

 

I'm already in Penang, out of Thailand with the old passport, in to Malaysia with the new one. No questions asked

1 hour ago, 11223344 said:

Yes, not even the Embassy in Bangkok can cancel my passport. It has to be sent back to my country.

 

I'm already in Penang, out of Thailand with the old passport, in to Malaysia with the new one. No questions asked

Although not an issue in your case, this might be for your compatriots who would need to have extension of stay stamps transferred from old to new passports. Immigration will not normally perform this task unless the old passport had been formally cancelled first.