As @KennethThas noted, Thai chilis are not traditionally used in Chinese cuisine. In fact, I would strongly caution against doing so.They are far hotter and have a different flavor than the traditionally used varieties in Sichuan. If you subbed them for the Sichuanese varieties in the same quantities, you would have mapo inedible.
The traditional chilis used in Sichuan are 朝天椒 (cháo tiān jiāo), 'facing heaven chilis' or the similar 七星椒 (qī xīng jiāo), 'seven star chilis'.
Dried Facing Heaven Chilis - 朝天椒干 (cháo tiān jiāo gān)
They are used pickled and dried (whole and ground).
豆瓣酱 (dòu bàn jiàng), 'chili bean paste', sometimes transliterated as 'toban-djan' is also used. It is made using 二荆条辣椒 (èr jīng tiáo là jiāo), erjingtiao chilis, another common, distinctive tasting chili in Sichuan.
Mapo Tofu normally only contains the chili bean paste and (only sometimes) ground dried facing heaven chilis.