By Kyu-seok Shim

SEOUL, May 22 (Reuters) - Samsung Electronics' ( SSNLF ) workers in South Korea on Friday began voting on a pay deal that ensures huge bonuses for its memory chip workers, but other employees who didn't fare as well said they plan to oppose it.

The 11th-hour government-mediated agreement reached this week averted a planned 18-day strike in a win for the company as well as the South Korean economy.

But the deal primarily benefits workers in Samsung's memory chip business which has seen profits soar amid the AI boom. Some of those workers are set to receive bonuses of about $416,000 this year.

Workers in its foundry and logic chip units will receive much smaller but still substantial bonuses, while those employed in other divisions like smartphones and home appliances will receive even smaller bonuses.

"This round of negotiations has effectively been reduced to bargaining over bonuses for the semiconductor memory division," Lee Ho-seop, a leader of the National Samsung Electronics Union (NSEU), told a news conference on Friday, adding that "a rushed outcome was produced."

Some 89,000 workers are expected to cast their ballots in the voting, which is being conducted electronically and runs until 10:00 a.m. on May 27.

The negotiations were led by a representative from Samsung's chip division, who has said he expects the agreement to be ratified. His union bloc, known as the Samsung Electronics Labor Union (SELU), boasts around 70,000 members.

The NSEU has around 19,000 members.

A separate union, the Samsung Electronics Co Union (SECU), also attended the Friday press conference.

It was not immediately clear if its members - who include both chip workers as well as non-chip workers - were eligible to vote as disagreements with the other union blocs caused the SECU to leave the negotiating team before an agreement was reached.