The official waved Moult away and soon gave a spot-kick at the other end when Scott Sinclair went down under the attention of Cedric Kipre, who was shown a straight red card.
Moussa Dembele converted to add to James Forrest’s 49th-minute opener and put Celtic 2-0 up. That was the way the game finished after Moult hit the post with a late free-kick - and the forward was aggrieved at referee Thomson’s display.
“I’m gutted he hasn’t given me a penalty,” Moult said. “It’s a stonewaller on me. I’ve got a tap-in, why would I go down? I think it’s Tierney, he tries to pull me back, doesn’t manage to grab my shirt and then clips my heels.
“I’ve had a look at it and I can see him trying to pull me back and then he clips my heels. Whether he meant to clip my heels I’m not sure, but he definitely makes contact with me. Like I said, why would I go down? I’ve got a tap-in.
“They go up the other end and Sinclair goes down and he gives a penalty and sends our lad off when we’ve got two men defending behind Cedric. So why is it a sending-off and why is it a penalty?”
When asked what Thomson said about his appeal, Moult said: “He wouldn’t let me speak to him. He just ran off.”
Sinclair defended himself after going down in the left channel from what looked the slightest of contact from the arm of Kipre, who was deemed to have denied an obvious goalscoring opportunity.
“I felt a tug on my arm and I went down,” the Celtic winger said. “The defender pulled my arm and I went down for it.”
Motherwell had restricted Celtic to one headed chance for Dembele in the first half but Sinclair felt his side’s winning mentality shone through as they clinched a fourth consecutive domestic honour.
“We just want to win games,” he said. “That’s what we stick to - the winning mentality and just being relentless and keep winning.
“That’s the thing when we play these sorts of games, to be as patient as we can. Sometimes it gets to the hour mark and they get tired and that’s when we open up the game.”
Moult was also left to rue a world-class stop from Craig Gordon to prevent him levelling with a header.
“I felt like we were in the game, even when they went 1-0 up,” he said. “Gordon has made a great save from a header.
“As soon as I headed I thought I had got a good contact on the ball and hit it pretty hard. Fair play to him, it’s a good save.”