I am a dual citizen of the UK and South Africa. Currently I'm in Thailand on the UK passport.

I am interested to leave Thailand and enter Malaysia on the UK passport and then re-enter Thailand using the South African one (much more pages in this one...).

I would be grateful if anyone knows if this would be allowed?

Thank you!

You can only do this if you leave and re-enter by air. (At land borders they will check for the exit stamp of the other country).

If you go by air, OK

By land, not OK.

on top of that, Malaysia doesn't even recognise the concept of dual nationality. Possibly the worst place to even try it.

As others have said, fly.

on top of that, Malaysia doesn't even recognise the concept of dual nationality. Possibly the worst place to even try it.

As others have said, fly.

Very true. People have gotten into trouble in Malaysia simply because they were spotted with double passports.