Chaucer’s Tale of Sir Thopas is told in a thumping rhyme scheme and song-like meter. Fair Sir Thopas, says Chaucer, lived in Flanders. He was a brave knight, with a white face and lips red as a rose. His beard was bright yellow and he wore expensive clothes. He is good at hunting, archery, and wrestling. All the young ladies swoon over Sir Thopas, but he remains chaste.
Chaucer tells the tale of Sir Thopas in a bob-and-wheel rhyme scheme, which makes it sound like childhood doggerel ("doggerel" is low-quality poetry). Young Sir Thopas is a fair, handsome knight, much like the Squire, and he is trained in the general arts of a knight, including chastity.
Sir Thopas goes out riding with his sword by his side one day in springtime, when all the flora and fauna are in heat, and he is filled with “love-longynge” when he hears birdsong. Thopas rides until he is weary and falls asleep on the grass.
Even though Sir Thopas is chaste, all the flowering and birdsong of springtime make him half-crazy with unfulfilled love and, presumably, lust.
Sir Thopas dreams of an elf-queen who will be his mistress, since no earthly woman is worthy of his affections. Upon awakening, he determines to find this queen and rides onward through the woods. Sir Thopas runs into the giant Sir Olifaunt, who says that he protects the elf-queen. They agree to fight the next day, and Sir Thopas returns home.
None of the mortal women who pursue Sir Thopas are worthy of his charms: the only lady he wants to pursue is the elf-queen. This childlike rhyme, like the Wife of Bath’s Tale, is set in fairyland in the time of King Arthur.
Chaucer describes in great detail Sir Thopas’s preparations for battle. First, he eats sweets, and then he puts on layer after layer of fine clothes and armor.
The description of how Sir Thopas prepares for battle is a parody of the battle preparations in the Knight’s Tale, though this parody operates at the level of the author rather than Chaucer/narrator. In other words, it's just a part of the Chaucer/narrator's story, but in the larger context of the Tales it operates as a parody.
Lords and ladies, says Chaucer, listen to my story! Men speak of all the knights of Arthurian legend, but Sir Thopas is the most chivalrous of all. He has so many adventures that he barely ever sleeps in his house. One day––
Chaucer excitedly describes Sir Thopas as the most daring, noble knight of them all, but just as he beginning to launch back into his adventure, the Host interrupts him…