The lodge's chairman Lee Bock Guan said he was sure the money came always from the same unknown donor.
"You know it is the same person, because the notes always come in the same, neat stack," the report quoted him as saying.
The lodge had no plans to pursue the identity of the mysterious donor as it was obvious the person prefers to stay anonymous, he added.
"He or she could easily have written a cheque. By donating in cash, this person clearly prefers to be unknown," Lee said. "We thank this person but have no interest in discovering his or her identity."
The lodge has been providing free vegetarian meals to the less-privileged for more than 20 years, the report said.
It spends 210,000 Singapore dollars per month on its daily buffet and plans to spend even more, as more people came forward for help.