Moving right to left is a bit easier to get into the tunnel. Land aiming down approximately 3 pixels inside the rightmost tile. If Samus is too far right she will fall out, too far left and a thorn pushes her out, not aiming down puts her stuck in crouch. Then spinjump left to take a thorn hit and get wedged in the ceiling. Then start the crawl while taking constant thorn damage. Perform one jump per thorn hit. Note that if Samus is hit by the thorn before landing, aiming down is not necessary. Note that a downback may be helpful to get into the tunnel: stand fully on the left side of the nearby ledge and run off then start and hold a downback to land in position.

Requires:

{
  "notable": "Spikeway Tunnel Crawl"
}
"canTunnelCrawl"
"canTrickyJump"
{
  "thornHits": 31
}
{
  "obstaclesCleared": [
    "A"
  ]
}