One of the suspects is a 25-year-old man who was taken into custody in Thailand earlier and has since returned to Hong Kong.
Officers said he was arrested near Pattaya and sent back to the SAR on Tuesday.
Police believe he was one of two people who carried out the attack.
On Wednesday afternoon, the suspect was taken to Fo Tan where officers reconstructed the case.
Officers said he will be charged soon.
Police also revealed that two others were arrested earlier on suspicion of assisting offenders.
So far, eight out of the nine suspects linked to the case have been arrested by Hong Kong or mainland police, including a 76-year-old man and his son who allegedly planned the attack.
Speaking in a media briefing, superintendent Li Muk-yik said the remaining suspect, who allegedly served as a lookout, had fled to the mainland and remains at large.
He also said the force was able to identify all the suspects after going through surveillance cameras.
Li added that the probe has been challenging.
“The suspects [allegedly] put fake licence plates on taxis [as they fled]. They were very cautious before and after the incident,” he told reporters.
“They had [allegedly] changed their clothes and the vehicles several times after they fled.”
Li said the case was triggered by disputes over money.
