Ratchaburi cruised to a 3-0 victory over Army United on Saturday to open up a three-point gap at the summit, Douglas Rodrigues and Assadin Mungkud finding the net either side of an Heberty penalty.
However, Singhtarua - promoted to the top flight at the end of last season - moved back level with Ratchaburi 24 hours later courtesy of a last-gasp 1-0 victory at Chainat.
Muang Thong United failed to return to winning ways after their 2-1 home defeat to Ratchaburi on Wednesday and were reliant on a stoppage-time Jay Bothroyd strike in a 1-1 draw with BEC Tero Sasana.
Bothroyd cancelled out Peerapat Notchaiya's 71st-minute opener and there was still time for BEC Tero Sasana's Gilbert Koomson to receive his marching orders for a second bookable offence.
Chonburi are carving out a reputation as the division's draw specialists, and recorded their fourth stalemate in six matches with a 2-2 result at PTT Rayong on Saturday.
Rayong held a 2-0 lead at the break, but their visitors battled back well with late goals from Chakrit Buathong and Anderson Dos Santos.
Samut Songkhram remain winless at the foot of the table following a 3-1 home defeat to Suphanburi, while Songkhla United picked up their first win of the campaign, beating Sisaket 2-1.
Elsewhere, TOT registered a 2-0 win over struggling Bangkok United, and Chiangrai United and Buriram United shared the spoils in a 1-1 draw.
Police United were on the receiving end of a 2-1 result at home to Osotspa, and Bangkok Glass triumphed 2-0 over Air Force Central.
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