As of 3rd January 2023, the entry restrictions for Spain related to COVID-19 have been lifted. Singaporean travellers are no longer obligated to show their vaccination certificate or submit to a coronavirus test upon arrival, except for those coming from China.
However, it is best to remember that the travel situation post Covid-19 is constantly evolving. Make sure to refer to Spain’s official government page on Covid-19 entry requirements for the latest information.
Singapore’s Ministry of Foreign Affairs webpage also provides a comprehensive guide for matters related to travelling to Spain.