The male suspect was arrested at a border-crossing with Cambodia while trying to cross the border.
Thai Police spokesperson Prawuth Thavornsiri is describing the man as "a main suspect."
"At this early stage all evidence confirms that he is a main suspect in the same gang as the suspect we arrested earlier. And he is also one of the people who brought the bomb to the target sites; both sites."
Another foreign national is currently being held after being arrested in Bangkok on Saturday.
Both are considered suspects in the blast at the popular Erawan Hindu shrine in Bangkok just over 2-weeks ago that left 20 people dead, including 7 Chinese nationals.
Thai authorities have been interrogating the suspect arrested this past weekend, describing him only as a 28-year-old man.
They have yet to release his name or nationality.
Thai authorities say bomb-making materials and over 200 forged passports were found at the apartment where he was detained in the outskirts of Bangkok.
But, at this point, it is unclear whether either of the two arrested men is the suspect seen on a close circuit security camera leaving a backpack at the shrine just minutes before the blast on August 17th.
Police also raided another apartment in the outskirts of Bangkok on Sunday where they found more bomb-making materials.
Thai Military spokesperson Pareya Netrawichien says Thai authorities have now issued a total of seven arrest warrants.
"The court has issued arrest warrants for the four suspects namely, one, a man in yellow shirt who may have been involved in the Ratchaprasong incident; two, a man in blue shirt who may be related to the incident at Sathorn pier; three, a man as seen in the sketch who has been seen to have stayed in a rental room in Minburi area. The officials have found explosive components and equipment in his room. Four, Miss Wanna Suansan, who signed rental contracts for several rooms in Minburi area, the man in the sketch has stayed in one of those rooms."
But a female suspect who identified herself as a 26-year-old Thai Muslim woman Wanna Suansan had since contacted Thai authorities to give a statement.
Also on Tuesday, Thai police transferred 16 men - including senior officers - from their posts in Bangkok districts amid accusations of negligence.
The immigration chief and five others have also been transferred from their posts in Sa Kaeo, near the Cambodian border, where Tuesday's arrest took place.
The motive behind the August 17th bombing - uNPRecedented in its scale in Thai history - is still unknown.
