In Taigi, 骰子 tâu-á, 骰九 tâu-káu, 撚骰 lián-tâu, 骨骰 kut-tâu, 十八仔 si̍p-pat-á, 十八骰仔 si̍p-pat-tâu-á.
【廣韻】度侯切【集韻】【韻會】【正韻】徒侯切，𠀤音頭。骰子，博陸采具。So it is the name of a dice, a gambling tool, since the Tang dynasty, and the character is supposed to sound the same as the character 頭.
There’s no way for 骰 to be pronounced as shaǐ. Someone just kunyomied a non-Mandarin pronunciation for 色子 on the characters 骰子.