The Dutchman was on the bench for the Villains against Southampton, and Lambert has said his return to the starting side will be “huge” for his relegation-threatened team.
"Ron is okay for tomorrow,” he told the club’s official website. “He's come through this week. He's been fine.
"It's important to have him back. He's been out for a couple of months. No-one thought it would be that length of time.
"Ron coming back will be a major plus.
"The only thing he's lacking is match fitness. But with his muscle and the way he is, he's fine. His return could be huge.
"He was playing really well until he was injured and it will be good to have him back."
Meanwhile, Darren Bent and Richard Dunne are also close to making comebacks for the Birmingham side, although Lambert is reluctant to throw the pair into action too soon.
|11/5||Darren Bent is 11/5 with Bet365 to score anytime against West Brom on Sunday|
He added: "Darren's been out with his knee. He will train today hopefully. We will monitor him a bit. I have to look how Darren is feeling. We have three games in a week so I'll have to see how he's feeling.
"Richard will train today which is great news. He has not done very much for the last half year or so.
"Hopefully Richard has been cured and Darren can get back quickly. There are one or two still injured but there are one or two back."