Can anyone explain the difference between 'tammadaa' and 'daam tammadaa' for me? My Thai teacher seems quite unable to do so. I always assumed that the difference was that the first meant 'usually' and the second 'as usual', but the examples that my teacher has come up with do not bear this out. From her examples I can detect no clear rules about usage at all.

ธรรมดา - (tammadaa) is the adjective 'ordinary' ตามธรรมดา - (dtaam tammadaa) is the adverb 'ordinarily'. Literally, 'to follow the ordinary (way).

ตามปกติ seems to be a bit more common though.

ตามธรรมดา can also mean like usually if u talk about sth u do daily

Thanks for the replies. It looks like I've been getting myself into a twist over something pretty straightforward. Would it be correct to say that 'bpokkati' can serve as both adjective (usual) and adverb (usually)? If I want to say 'as usual' (eg 'I will see you tonight as usual'), I have been told that 'dtaam khuhy' or 'chen khuhy' is the way to express it. Agreed?

Thanks for the replies. It looks like I've been getting myself into a twist over something pretty straightforward. Would it be correct to say that 'bpokkati' can serve as both adjective (usual) and adverb (usually)?

I feel it's more correct for the word ปกติ on it's own to act as an adjective and the phrase ตามปกติ to work as an adverb. However, I have seen ตามปกติ used as an adjective.

You will hear some people say "ปกติแล้ว" at the beginning of a sentence to be translated as "usually." It's really just a shorthand way of saying ตามปกิตแล้ว or โดยปกติแล้ว.

If I want to say 'as usual' (eg 'I will see you tonight as usual'), I have been told that 'dtaam khuhy' or 'chen khuhy' is the way to express it. Agreed?

From the context of this sentence, I think it would be better to use เหมือนเดิม or เช่นเดิม in this case. พบกันคืนนี้เช่นเดิม