Mohbat Thakor (35) was arrested along with three others on June 19 in connection with theft of Rs 32 lakh cash from a dry fruit packaging unit located at Udhna industrial area.
A local court had yesterday remanded him to police custody till June 27, they said.
"Early this morning, Thakor complaint of respiratory problem and collapsed. It appeared that he had suffered a heart attack, after which he was immediately rushed to a hospital where he was declared brought dead," Surat DCP Jagdish Patel said.
Police had recovered over Rs 14 lakh from Thakor's possession, the DCP added.