After 17 matches, the Fire Dragons have 35 points, one ahead of SCG Muang Thong, who have a game in hand.
Muang Thong will regain the lead if they avoid defeat at Si Sa Ket today.
Bangkok Glass striker Chatree Chimtalay shocked BEC Tero after 18 minutes only for Japanese Sho Shimoji to equalise a minute later.
In an entertaining match, both sides could have won with Bangkok Glass forward Teerathep Winothai having the best chance in the second half.
Holders Buriram United continued their revival with a 3-0 win at Chainat. Carmelo Gonzalez scored twice at 29 and 48 minutes and Javier Patino completed the rout from the spot in injury time.
Buriram are third on 30 points, five behind leaders BEC.
Songkhla United boosted their survival chances with a 2-1 home win over Chiang Rai United.
Phichitphong Cheuichiu gave the visitors the lead in the 12th minute but Kayne Vincent equalised for Songkhla moments later. Pornsak Pongthong scored the winner for the Fighting Bulls six minutes from time.
Police United suffered a 2-1 home loss to bottom side Samut Songkhram.
The visitors raced to a 2-0 lead through Samuel Ajayi and Kato Yusuke, and Michael Murcy pulled a goal back for the hosts.