Commercial services began on the Red Line on Monday after four months of trial operation, with fares ranging from 12-42 baht.
To improve passenger experience, the line's operating hours have also been extended, with services running to midnight every day.
The director-general of SRT Electrified Train Co, Suthep Panpeng, said ridership will initially decline by 20% to around 8,000 a day given the end of free services, though the figure is expected to increase within a couple of weeks.
A similar drop was seen when the trial period ended for the Airport Rail Link (ARL), which went into commercial service on Aug 23, 2010. After three months, however, ridership recovered.
Around 30,000 people per day will travel on the Red Line next year, Mr Suthep said.
At Bang Sue, the Red Line branches into two sections, with services to Rangsit running on the northern line and services to Taling Chan running on the western line.
Mr Suthep said initially, five trains will be deployed on the longer northern run and four trains on the western section.
On the Bang Sue-Rangsit section, a train will run every 12 minutes from 7am-9.30am and 5pm-7.30pm and every 20 minutes outside peak hours. Meanwhile, on the Bang Sue-Taling Chan section, a train will depart every 20 minutes throughout operating hours.
Mr Suthep said the shortened headway means there will be 138 trips along the Bang Sue-Rangsit section, as opposed to 88 during the trial period.
Meanwhile, there will be 112 trips per day on the Bang Sue-Taling Chan section, up from 64 trips per day.
The director-general insisted health and safety regulations will be strictly enforced.
Staff will also regularly check rail signalling equipment, following reports of thefts earlier.
Mr Suthep added that the company will work to ensure punctuality and safety.