If you are from middle east, there is no problem to face the temperature. only thing is to be aware of high humidity.
1st day - land in Kuala Lumpur , capital city of Malaysia, spend a day in city .
2nd day - goes to Malacca , 3 hours drive away to enjoy the old tradition town life;
3rd day come back to Kuala Lumpur and goes to Genting Highland to relax for the temp about 20 degreec C.
4th day - fly to Bangkok, Capital city of Thailand. stay 2 nights ther a have a glimpse
5th day - in Bangkok
6th day - fly to Chieng Mai and spend 2 nights
7th day - stay in Chieng Mai.
8th days - fly back home

If you have 8 days, the above is fine. If you only have 7 days , take off the 2nd day trip .
Hop you can finfd this useful.