Hi,i am malaysia wife is thai,baby born in thai,

need to apply thai and malaysia passport for my baby,if have both passport,when in thai custom only show thai passport and when in malaysia custom only show malaysia passport,is that any problem?appreciate anyone can answer my question

Do not believe Malaysia allows dual nationality so could be a serious problem. Being born in Thailand would not make your child Thai unless father is Thai (it is not like Malaysia where place of birth equals nationality). You may need legal advise and base decision on where you plan to live for now.

Mother is Thai, so child is a Thai citizen.

Dual Nationality is the issue for Malaysia:

http://en.wikipedia.org/wiki/Malaysian_nationality_law

Not sure how effective is the Malaysian government in checking that babies don't have another citizenship ...

Sorry read it to be "I am Malaysia wife" rather that wife is Thai but the dual nationality issue remains an issue for Malaysia.