Never take a bus to Alor Setar to cross border from Thailand… unless you are pretty confident of things.
You do not get a satisfactory or complete answer however hard you try to find on net, in forums, twitter and everywhere else about taking a bus from Hat Yai to Alor Setar, a comparatively less popular place in northern Malaysia. Try in Hat Yai. Go to bus station (also known as Bor Kor So)….
No direct bus for Alor Setar. Even though the place is big enough to have an airport, a railway station and is quite a developed town of Malaysia. Bigger than Ipoh for all practical purposes.
Do not get carried away if in Thailand they promise to drop you at Alor Setar. Because in reality no one knows anything about it. It’s in a different country, you see.
From southern Thailand,