I have let my dtac sim run out of credit and now they have disconnected the number is there anyway that the number can be put back on it has been disconnected for about 3 months

If you are in Thailand perhaps a visit to a DTAC full service shop is in order. Chances are your number has been recycled - there is a bit of a number shortage, and is in use by someone else. If not, maybe they can give it back to you?