github-actions get branch name or PR number for deployment_status event

I am trying to trigger our smoke tests after deployment is completed. Deployment could be done via any platform like vercel, GitHub, etc. I am listening for the deployment_status event from GitHub actions and if it is success, I get the PR details based on github.sha. Code as below:

name: Run Cypress Smoke Tests

on: [deployment_status]
....

steps:
- name: GitHub API Request
  uses: octokit/request-action@v2.x
  id: octokit
  with:
    route: GET /repos/:repository/commits/:commit_sha/pulls
    mediaType: |
      previews: 
        - antiope
        - groot-preview
    repository: ${{ github.repository }}
    commit_sha: ${{github.sha}}
  env:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

But sometimes github.sha is not correct. I get the value of commit ID from the merge branch instead of the actual repo as mentioned https://github.community/t/github-sha-not-the-same-as-the-triggering-commit/18286/2.

How do I get the correct branch name or PR number or commit ID for the deployment_status event?

Thanks in advance.