I will be in phuket and the area and need to change my visa by may 4th. was thinking probably Malaysia. Please advise the cheapest and most convenient way to do this Thank you, Luis

If you mean a 30 day visa exempt entry you would have to check flights. But if 30 days might not be enough getting a tourist visa might be more cost effective as you must leave anyhow.

If you have a tourist visa and need to extend 30 days you do that at local immigration office.