The former chief technology officer of ride-booking app Grabtaxi is suing the company, claiming he is owed around $2.3 million in shares following his departure last year.

Mr Zhu Wei claims that, under his departure terms, the company offered to issue him 22,566 ordinary shares in the parent company Grab Inc.

However, he did not accept the offer as the terms also imposed a series of restrictions which he claims were not indicated in his original employment terms. These detailed the compensation package to be given in the event he left before completing four years of service.

At issue in the case is whether there were valid conditions attached to the issue of the shares or whether they were to be given to Mr Zhu unconditionally.

Grabtaxi Holdings is denying the claims in defence papers filed, pointing out the share issue was subject to rules of the Grabtaxi Share Option Plan.

A High Court pre-trial conference was held yesterday.

Grabtaxi, Uber's chief rival in this region, set up a US$100 million (S$136 million) research and development hub here in April last year, armed with the firm's top engineers and data analysts to develop new products and find ways to improve its cab booking service.

Mr Zhu, an American software engineer whose previous experience included heading the Facebook engineering team that developed Facebook Connect, was hired as chief technology officer of the global Grabtaxi group of companies in August 2014.

But he left a year later and while he had no dispute about the monetary compensation as part of the departure terms, he took issue with the conditions attached to the share issue offer that was included as part of the package.

The shares were subject to him signing the Grab Inc 2015 Equity Incentive Plan which required him to forgo his rights to equity compensation under his employment terms. The conditions also required that he vouch to exercise voting rights accruing to the Grab Inc shares in accordance with the instructions of Grabtaxi group chief executive Anthony Tan.

Mr Zhu, represented by lawyer Ronald Choo from Quantum Law Corp, claims in court documents filed that the employment terms did not restrict him in such a manner, arguing he is not obliged to accept the share offer in Grab Inc, and that he is seeking his entitlement in the ordinary shares from the share capital of Grabtaxi Holdings. He wants a court order for the share issue sought and damages from the delay in issue.

Allen & Gledhill lawyer Ramesh Selvaraj, in defence documents filed in March, countered that Mr Zhu was in effect seeking to get the shares free of any conditions despite having agreed to them under the employment terms.

The share option plan is the same as the equity incentive plan referred to by Mr Zhu which was offered to him at the time of departure last August, he added.

The company also indicated that the number of outstanding shares in Grabtaxi was less than when Mr Zhu joined, therefore the amount of shares in dispute is also smaller.

Mr Choo applied last month to amend his statement of claim to clarify this issue and add a second defendant to the suit, among other things.

A High Court hearing on his application is due next week.