The Bangkok heat is almost unbearable. 'This is nothing,' says the devil. 'Just wait until the hot season - now that's real torture!' An apprentice gremlin nods in agreement. It's not easy being a demon. Years of strenuous physical training do not make the slow and sweaty process of being sewn into a weighty costume any less gruelling. But it's a familiar ritual for the classical Thai dancers of the National Theatre in the heart of the city. After a full hour of attention from two assistants, a sparkling silver and scarlet demon flashes a spirited smirk and poses for photos before bounding off to unleash mischief on the capacity matinee audience. The gods and monsters of khon, traditional Thai dance drama, have been delighting Siamese audiences for the past seven centuries, although for the majority of its history those audiences were restricted to VIPs. Jarin Khaorungrueng, a khon instructor with the Thai Fine Arts Department, explains: 'In earlier times, khon was referred to as lakhon nai [inner theatre], which meant it was only performed within the royal palace. With the establishment of the National Theatre in 1960, the door was opened to the general public to witness this art of kings.' Khon consists of an exotic orchestra, the throaty yet strangely addictive melodies of old-style Thai singing and the booming voices of side-stage narrators, all accompanying brightly bedecked dancers as they frolic, strut and battle their way through adventure-packed tales. The curtain rises to reveal the green-faced Intorachit, son of demon king Totsakan. The princely demon bows before a white-bearded sage, begging in vain for super powers to use in his fight against the righteous. But Intorachit is a patient devil, so, as the curtain falls on the opening scene, he begins 'seven years' of meditation, to master esoteric mantras. Today, the dancers are men but originally, all khon troupes were made up entirely of women, explains Kanchana Khaorungrueng, a wardrobe attendant at the National Theatre for 25 years. In this visually spectacular art form, it is the vibrant masks that stand out. 'The mask is the spirit of khon,' says Kanchana's husband, Jarin. 'On seeing the mask we understand the character's personality. There are six different categories of masks: angels, sages, humans, demons, monkeys and mythical animals ... Everything is contained in the detail.' Intorachit's 'seven years' in silence have inspired the gods to grant him magical powers. And soon he declares war on the god Indra. From atop his golden chariot, Intorachit leads his army of rogue warriors against the hapless deity and a stylised skirmish follows. These entertaining antics were first scripted two millennia ago by Indian poet Valmiki, when he composed the epic Ramayana. In 1807, Phraphutthayotfa Chulalok, the Siamese king, lengthened the Sanskrit original by 25 per cent (to make a total of 60,000 stanzas) and added many uniquely Thai ingredients to create the Ramakian - Thailand's foremost literary masterpiece. The result of this majestic writing spree is the swashbuckling tale of heroic Prince Rama and his allies, and their universe-rattling battle with the villainous demon king Totsakan and his unruly cohorts. The sparsely set stage welcomes the rambunctious Intorachit's return, fresh from his victory over Indra. It's time to pay Rama a surprise visit. Rama appoints his brother Laksman to command the royal defences. A climactic brouhaha is brewing. Martial music rocks the battlefield as Intorachit and Laksman exchange dramatic blows. Our swaggering demon is resolute until agile Laksman delivers a strike that sends Intorachit reeling. The irrepressible Intorachit then unleashes his secret weapon - the Nakhabart. The 'serpent arrow' summons forth a nest of snake-headed actors bearing scaly vipers (from the props department, of course) that constrict Laksman and his troops into slithering submission. Rushing to the aid of his unconscious sibling, Rama displays some impressive wizardry of his own. Intorachit beats a hasty exit to the accompaniment of a hearty ovation. But before entering the wings, he pauses, slowly pivots, looks Rama in the eye, and lets fly a final flurry of finger-pointing that clearly says, 'This is not the end!' Getting there: Thai International Airways ( www.thaiairways.com ) flies from Hong Kong to Bangkok. The National Theatre is on Na Phra That Road (near the Grand Palace). Khon performances take place on the last Friday and Saturday of each month. Call the theatre on: 66 2 224 1342.