You may even be pushed for time. KL immigration is pretty slow with everybody being finger printed inc children. The train go's around every 15 minutes and takes around 10-15 minutes between terminals

Different terminals. Thai use KLIA1 You'll need to use the shuttle train. Its 2 ringget.

Air Asia flys in and out of KLIA2. I've no idea what Terminal M is?

Is your return flight in the same Terminal? Some airlines use KLIA1 some use KLIA2

KL is a big airport. The gates are not linked together. I use KL a fair bit.

I've never yet been able to stay airside while on a transit involving 2 airlines. I've always had to clear security and immigration then check in to the airline desk and go back through. Different if your with the same airline. It also makes a difference on what time your return next flight is. They mostly dont want you hanging around airside for hours.

I can't see it working. You would already be airside and attempting to board without even being added to the APL list.

Would that work though what he wants to do by coming back on a different airline? He wouldn't even of cleared the airlines security.

Unless your Japanese or have the residents card, I don't believe any visa is possible in Japan

For non-Japanese applicant, a copy of residence card or certificate of alien registration which is valid at least 3 months or more. For those who are currently applying for renewal of residence card, please submit a copy of acceptance of renewal issued by Immigration Bureau of Japan. The applicant is also required to present the original documents of identification upon visa application.