"Sorry to hear about Bala Saheb's sad demise. Never accepted his Political Ideology but admired his Wit and Courage of Conviction," he tweeted.
He retracted immediately, saying "My apologies to Thakre Family Pray for his speedy recovery"
Later taking to media, Singh said: "I pray to God to improve Bal Thackeray's health, he has fought against the world, I am sure he will fight for his health.
Meanwhile, Bharatiya Janata Party (BJP) leader Gopinath Munde who visited Thackeray's residence 'Matoshree' this morning told media that the Sena chief's health is better than last night.
Earlier, Thackeray's son Uddhav Thackeray appealed for calm to those assembled outside their residence.
He said, "Balasaheb has strong will power. We will come out of this problem. Don't trust rumours. Make peace we are hopeful. You should be hopeful as well. Let's pray for Balasaheb."