The seiko 7s36 23J movement is inherently not very accurate, so unless yours is running super fast or super slow (like more than a minute a day or worse) then I would not bother getting it regulated. If regulation, oiling + water resistance testing is needed, maybe Thong Sia is the best bet but it may take ages before you get your watch back (weeks usually). And if it is just chnaging the back case gasket, then any big watch shop can do it, or try that watch accessories shop at Jalan Sultan (Selangor Complex) ground floor but the 2 ladies (wo)manning the counter can be realy unfriendly sometimes.
