Is my plan for a 4-month stay in Thailand using a tourist visa feasible?

I’m due in Thailand november 21 till march 20,accomadation all booked so correct me if I’m wrong as it’s been 5 years since a lengthy trip as this I should apply for tourist visa 60 days with the option to extend a further 30 days at immigration and then fly short haul ie Laos or Cambodia and upon return have a visa free 30 day stamp issued upon arrival back into Thailand to take me up to four months cover of stay to satisfy immigration requirements,thanks in advance for any help