▲是的，be supposed to与be thought to都是固定搭配，但它们的意思不同：

1. be supposed to do sth 应该……，必须……

No one was supposed to know about it. 不应该有人知道此事的。

We are supposed to meet her at the train station. 我们得去火车站接她。

You’re supposed to pay the bill by Friday. 你最晚在星期五结清这笔帐。

They were supposed to be here an hour ago. 他们应该在一小时以前到达这里。

2. be thought to do sth 被认为……

At school he was thought to have an attitude problem. 上学时他被认为态度有问题。

Diamonds were once thought to have magical powers. 钻石曾一度被认为具有魔力。

He’s thought to be one of the richest men in Europe. 人们认为他是欧洲最大的富翁之一。

Land animals are thought to have developed from sea animals. 陆地动物被认为是从海洋动物进化而来的。

▲你的句子意思：

What are you doing out of bed, Tom? You’re supposed to be asleep. 汤姆，你起床做什么？你应该是睡觉了。