Taiwan Styrene Monomer Corporation — Proxy Solicitation & Information Statement 2026

Apr 22, 2026

Taiwan Styrene Monomer Corporation

Meeting Notice for 2026 Annual Shareholders' Meeting
(Summary Translation)

I. The 2026 Annual Shareholders' Meeting (the "Meeting") of Taiwan Styrene Monomer Corporation (the "Company") will be convened at 9:30 a.m. on Monday, May 25, 2026 (shareholder registration will start at 9:00 a.m. at the venue of the meeting) at Conference Room on the 8th floor, International Convention Center of Chang Yung-Fa Foundation (No.11, Zhongshan S. Rd., Zhongzheng Dist., Taipei City, Taiwan).

Shareholders' meeting will be held by means of physical Shareholders' Meeting.

The agenda for the Meeting is as follows:

1. Report Items
   (1) 2025 Business Report
   (2) 2025 Audit Committee’s Review Report

2. Adoption Items
   (1) To adopt 2025 Business Report and Financial Statements
   (2) To approve the Appropriation of Profit or Loss of 2025

3. Extemporary Motions

II. Where the subject of the shareholders' meeting to be convened includes any contents that shall be explained in accordance with Article 172 of the Company Act, please visit the English website of the Market Observation Post System (MOPS) (https://mops.twse.com.tw) and go to Electronic Books > Shareholders' meetings to search for more details.

III. Pursuant to Article 165 of the Company Act, the registration of stock transfers will be suspended from March 27, 2026 to May 25, 2026.

IV. In addition to MOPS, the Company shall also send a hard copy of the aforementioned information, along with an attendance card and a power of attorney. We hope the shareholders would take the time to attend the meeting. If the shareholder opts to

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attend in person, please fill in the third form of the attendance card (the third form doesn't need to be mailed back) and bring along to the Shareholders' Meeting. If the shareholder opts to appoint a proxy, please fill in the sixth form, i.e. the power of attorney, and mail back the entire set of forms. Please ensure that the mail reach our stock transfer agency, Concord Securities Corporation (stock transfer department) five days before the Shareholders' Meeting. Concord Securities Corporation shall stamp on the attendance card and mail it back to the shareholder or the proxy appointed. The attendee must bring along the attendance card when attending the Shareholders' Meeting.

V. In event that there are solicitor of proxies, the Company shall compile and upload the information of the written proxy solicitation documentation to the Securities and Futures Institute website (http://free.sfi.org.tw) before April 24, 2026. On the website, investors should key in the stock code/abbreviation of the Company into the "Power of Attorney Query System" for more information.

VI. Shareholders could exercise their voting rights through STOCKVOTE platform of Taiwan Depository & Clearing Corporation (https://stockservices.tdcc.com.tw) during the period from April 25, 2026 to May 22, 2026.

VII. The Company has appointed Concord Securities Corporation Registrar and Transfer Agency Department to tally and verify the proxy forms collected for this shareholders' meeting.

Sincerely,

Board of Directors

Taiwan Styrene Monomer Corporation

This document is prepared in accordance with the Chinese version and is for reference only. In the event of any discrepancy between the English version and the Chinese version, the Chinese version shall prevail.