The former West Ham midfielder has been hit with the penalty after being found guilty of using foul and abusive language towards referee Iain Brines in the 1-1 draw with Celtic
The former West Ham captain was furious with referee Iain Brines in the 1-1 draw with Celtic at Parkhead earlier in November, when the official allowed Bhoys striker Tony Watt back on to the field in what he felt was a dangerous position after receiving treatment for an injury.
Despite Lomas apologising to Brines in person after the match, the SFA disciplinary committee found him guilty of using foul and abusive language towards an official, resulting in a six-match ban from the dugout.
However, Lomas also acquired a suspended two-match ban following another dismissal in the match against Ross County in September.
A statement on St Johnstone website read: "The SFA have handed Steve Lomas an eight-match touchline suspension following his dismissal from the dugout in the match against Celtic on November 11 for foul and abusive language towards a match official.
"This ban consists of six games for the offence committed at Celtic Park plus the suspended two-game ban which was already hanging over him following the game against Ross County in Dingwall in September."
Lomas faces yet more disciplinary action after being sent to the stands again towards the end of his side's 1-0 defeat by Hibernian on Wednesday evening.