Holding him or picking him up around the belly is very threatening to him. You should not pick him up that way until he is so tame that he will not bite you anymore.
Check out youtube for videos on how to tame a tokay. There is a lady named reptilewhisperer that has a great technique for taming a tokay so that it can be handled/held.
2.4.0 Crested geckos, 0.2.0 Gargoyle geckos, 0.1.0 Okeetee cornsnake - Correen,
0.1.0 Amel cornsnake - Fiona, 1.0.0 Snow cornsnake - Kai, 1.1.0 Kenyan sand boa, 1.0.1 Leopard gecko,
0.3.0 Guinea pig (Cavy) 5.1.0 Mutts, 0.2.0 Cats,
0.0.2 White-lipped (cheeked) mud turtles, 3.10.0 Bettas, 0.0.1 Rio grande gold tarantula