Ossumt,
If you plan on staying in Belize indefinitely, the easiest thing to do is simply buy a round trip ticket (fabricate the return date, it does not matter.) Then, simply stay in Belize and go about the monthly stamping process at Immigration here.
What's that....?
Oh, yes, of course, the $$$ for the return leg will have gone to waste, but trust that the longer you stay in Belize, that tix $$$ will soon be overshadowed by all the other ways in which $$$ seems to evaporate here in Belize!!!